Device to measure the solidification properties of a liquid film and method therefor

Abstract

The present invention is directed to an apparatus and a method for monitoring the viscoelastic properties, of a liquid film (e.g. coating). The apparatus comprises a substrate supporting a liquid film, a probe to contact the liquid film, means for effecting relative movement between the probe and the substrate and means for monitoring the resistance to movement of the probe in contact with the film to obtain a measurement of the solidification properties of the liquid film. This apparatus and method are particularly useful in comparing the effects of film formers, viscosity modifiers, solvents, and minerals on the drying rate of coatings at the early stage of film formation.

1. An apparatus for monitoring the viscoelastic properties of a liquid film comprising:
 (i) a substrate capable of supporting the liquid film, 
 (ii) a T-bar probe with a diameter from about 0.01 mm to about 2 mm mounted so as to contact the liquid film, 
 (iii) a means of effecting relative movement between the probe and the substrate so that the probe moves relative to the liquid film, and 
 (iv) a means of monitoring the resistance to movement of the probe contacting the liquid, 
 wherein the probe has sufficient surface area contacting the liquid film so that it may detect the resistance without interfering with the solidification of the liquid film. 
 
   
   
     2. An apparatus as recited in  claim 1 , wherein the substrate is a trough. 
   
   
     3. An apparatus as recited in  claim 2 , wherein the trough has a depth from about 0.005 mm to about 5 mm. 
   
   
     4. An apparatus as recited in  claim 1 , wherein the substrate is a flat plate. 
   
   
     5. An apparatus as recited in  claim 1 , wherein the means for monitoring the resistance of the movement of the probe is a transducer and the means for moving the substrate relative to the probe is a motor. 
   
   
     6. An apparatus as recited in  claim 1 , wherein the probe penetrates the liquid film and wherein the probe does not contact the substrate. 
   
   
     7. An apparatus as recited in  claim 1 , wherein the probe has a length from about 2 mm to about 50 mm. 
   
   
     8. An apparatus as recited in  claim 1 , wherein the probe has a length from about 5 mm to about 20 mm. 
   
   
     9. An apparatus as recited in  claim 1 , wherein the probe has a length from about 10 mm to about 15 mm. 
   
   
     10. An apparatus as recited in  claim 1 , wherein the probe has a diameter from about 0.025 mm to about 0.3 mm. 
   
   
     11. A process for monitoring the viscoelastic properties of a liquid film, wherein said liquid film is located on a substrate, wherein said process comprises the steps of:
 (i) contacting a T-bar probe with the liquid film; 
 (ii) moving the probe relative to the substrate so that the probe moves with respect to the surface of the substrate and in contact with the liquid film while the liquid film is solidifying; and 
 (iii) monitoring the change in the solidification properties of the liquid film, 
 wherein the probe has sufficient surface area contacting the liquid film to detect the change in properties without interfering with the solidification of the liquid film. 
 
   
   
     12. A process as recited in  claim 11 , wherein the probe penetrates the liquid film. 
   
   
     13. A process as recited in  claim 11 , wherein the substrate is a trough. 
   
   
     14. A process as recited in  claim 11 , wherein the substrate is a flat plate. 
   
   
     15. A process as recited in  claim 11 , wherein the moving of the probe is in an oscillating motion. 
   
   
     16. A process as recited in  claim 11 , wherein the solidification properties monitored are the change in viscosity of the film and the change in the elasticity of the film over time. 
   
   
     17. A process as recited in  claim 11 , wherein the probe does not contact the substrate.